ObstetricsTier 2Topic

Risk factors for common pregnancy-associated diseases - thromboembolism

Pregnancy as a hypercoagulable state

Pregnancy is a hypercoagulable state (physiological - increased clotting factors, decreased protein S, venous stasis from uterine compression) -> VTE risk ~4-5x baseline, highest postpartum

Leading direct cause of maternal death in high-income countries
Risk highest in the first postpartum week, but elevated throughout pregnancy and for 6 weeks postpartum

Virchow's triad in pregnancy: stasis (uterine compression of IVC/pelvic veins, immobility), hypercoagulability (raised factors VII/VIII/X/fibrinogen, reduced protein S), endothelial injury (delivery, especially caesarean)
Risk factors (RCOG risk-scoring approach): previous VTE, high-risk thrombophilia (antithrombin, protein C/S deficiency, homozygous/compound heterozygous factor V Leiden or prothrombin gene mutation), plus additive factors - age >=35, BMI >=30, parity >=3, smoking, gross varicose veins, current pre-eclampsia, immobility, multiple pregnancy, ART/IVF, caesarean delivery, prolonged labour, postpartum haemorrhage

Not a "diagnosis" itself - a risk assessment performed at booking, on admission, and postpartum
D-dimer is unreliable in pregnancy (physiologically elevated) - imaging (compression ultrasound, CTPA/V-Q) required if VTE is clinically suspected

Risk-stratified thromboprophylaxis with LMWH:
- Previous VTE or high-risk thrombophilia -> antenatal prophylaxis from early pregnancy
- >=4 risk factors -> prophylaxis from the first trimester; 3 risk factors -> from 28 weeks
- Postnatal: intermediate risk -> 10 days; high risk -> 6 weeks
Mechanical prophylaxis (compression stockings, intermittent pneumatic compression) if anticoagulation is contraindicated (e.g. active bleeding)

Antiphospholipid syndrome, inherited thrombophilias, multiple pregnancy, obesity

Risk remains elevated for the full 6 weeks postpartum, not only the delivery admission
Prior VTE in pregnancy substantially raises recurrence risk -> prophylaxis is required in subsequent pregnancies regardless of other risk factors

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